1 /* 2 * fs/signalfd.c 3 * 4 * Copyright (C) 2003 Linus Torvalds 5 * 6 * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org> 7 * Changed ->read() to return a siginfo strcture instead of signal number. 8 * Fixed locking in ->poll(). 9 * Added sighand-detach notification. 10 * Added fd re-use in sys_signalfd() syscall. 11 * Now using anonymous inode source. 12 * Thanks to Oleg Nesterov for useful code review and suggestions. 13 * More comments and suggestions from Arnd Bergmann. 14 * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br> 15 * Retrieve multiple signals with one read() call 16 * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org> 17 * Attach to the sighand only during read() and poll(). 18 */ 19 20 #include <linux/file.h> 21 #include <linux/poll.h> 22 #include <linux/init.h> 23 #include <linux/fs.h> 24 #include <linux/sched.h> 25 #include <linux/slab.h> 26 #include <linux/kernel.h> 27 #include <linux/signal.h> 28 #include <linux/list.h> 29 #include <linux/anon_inodes.h> 30 #include <linux/signalfd.h> 31 #include <linux/syscalls.h> 32 #include <linux/proc_fs.h> 33 #include <linux/compat.h> 34 35 void signalfd_cleanup(struct sighand_struct *sighand) 36 { 37 wait_queue_head_t *wqh = &sighand->signalfd_wqh; 38 /* 39 * The lockless check can race with remove_wait_queue() in progress, 40 * but in this case its caller should run under rcu_read_lock() and 41 * sighand_cachep is SLAB_DESTROY_BY_RCU, we can safely return. 42 */ 43 if (likely(!waitqueue_active(wqh))) 44 return; 45 46 /* wait_queue_t->func(POLLFREE) should do remove_wait_queue() */ 47 wake_up_poll(wqh, POLLHUP | POLLFREE); 48 } 49 50 struct signalfd_ctx { 51 sigset_t sigmask; 52 }; 53 54 static int signalfd_release(struct inode *inode, struct file *file) 55 { 56 kfree(file->private_data); 57 return 0; 58 } 59 60 static unsigned int signalfd_poll(struct file *file, poll_table *wait) 61 { 62 struct signalfd_ctx *ctx = file->private_data; 63 unsigned int events = 0; 64 65 poll_wait(file, ¤t->sighand->signalfd_wqh, wait); 66 67 spin_lock_irq(¤t->sighand->siglock); 68 if (next_signal(¤t->pending, &ctx->sigmask) || 69 next_signal(¤t->signal->shared_pending, 70 &ctx->sigmask)) 71 events |= POLLIN; 72 spin_unlock_irq(¤t->sighand->siglock); 73 74 return events; 75 } 76 77 /* 78 * Copied from copy_siginfo_to_user() in kernel/signal.c 79 */ 80 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, 81 siginfo_t const *kinfo) 82 { 83 long err; 84 85 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128); 86 87 /* 88 * Unused members should be zero ... 89 */ 90 err = __clear_user(uinfo, sizeof(*uinfo)); 91 92 /* 93 * If you change siginfo_t structure, please be sure 94 * this code is fixed accordingly. 95 */ 96 err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo); 97 err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno); 98 err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code); 99 switch (kinfo->si_code & __SI_MASK) { 100 case __SI_KILL: 101 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 102 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 103 break; 104 case __SI_TIMER: 105 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid); 106 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun); 107 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 108 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 109 break; 110 case __SI_POLL: 111 err |= __put_user(kinfo->si_band, &uinfo->ssi_band); 112 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd); 113 break; 114 case __SI_FAULT: 115 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr); 116 #ifdef __ARCH_SI_TRAPNO 117 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno); 118 #endif 119 #ifdef BUS_MCEERR_AO 120 /* 121 * Other callers might not initialize the si_lsb field, 122 * so check explicitly for the right codes here. 123 */ 124 if (kinfo->si_code == BUS_MCEERR_AR || 125 kinfo->si_code == BUS_MCEERR_AO) 126 err |= __put_user((short) kinfo->si_addr_lsb, 127 &uinfo->ssi_addr_lsb); 128 #endif 129 break; 130 case __SI_CHLD: 131 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 132 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 133 err |= __put_user(kinfo->si_status, &uinfo->ssi_status); 134 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); 135 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); 136 break; 137 case __SI_RT: /* This is not generated by the kernel as of now. */ 138 case __SI_MESGQ: /* But this is */ 139 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 140 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 141 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 142 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 143 break; 144 default: 145 /* 146 * This case catches also the signals queued by sigqueue(). 147 */ 148 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 149 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 150 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 151 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 152 break; 153 } 154 155 return err ? -EFAULT: sizeof(*uinfo); 156 } 157 158 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, 159 int nonblock) 160 { 161 ssize_t ret; 162 DECLARE_WAITQUEUE(wait, current); 163 164 spin_lock_irq(¤t->sighand->siglock); 165 ret = dequeue_signal(current, &ctx->sigmask, info); 166 switch (ret) { 167 case 0: 168 if (!nonblock) 169 break; 170 ret = -EAGAIN; 171 default: 172 spin_unlock_irq(¤t->sighand->siglock); 173 return ret; 174 } 175 176 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 177 for (;;) { 178 set_current_state(TASK_INTERRUPTIBLE); 179 ret = dequeue_signal(current, &ctx->sigmask, info); 180 if (ret != 0) 181 break; 182 if (signal_pending(current)) { 183 ret = -ERESTARTSYS; 184 break; 185 } 186 spin_unlock_irq(¤t->sighand->siglock); 187 schedule(); 188 spin_lock_irq(¤t->sighand->siglock); 189 } 190 spin_unlock_irq(¤t->sighand->siglock); 191 192 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); 193 __set_current_state(TASK_RUNNING); 194 195 return ret; 196 } 197 198 /* 199 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative 200 * error code. The "count" parameter must be at least the size of a 201 * "struct signalfd_siginfo". 202 */ 203 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, 204 loff_t *ppos) 205 { 206 struct signalfd_ctx *ctx = file->private_data; 207 struct signalfd_siginfo __user *siginfo; 208 int nonblock = file->f_flags & O_NONBLOCK; 209 ssize_t ret, total = 0; 210 siginfo_t info; 211 212 count /= sizeof(struct signalfd_siginfo); 213 if (!count) 214 return -EINVAL; 215 216 siginfo = (struct signalfd_siginfo __user *) buf; 217 do { 218 ret = signalfd_dequeue(ctx, &info, nonblock); 219 if (unlikely(ret <= 0)) 220 break; 221 ret = signalfd_copyinfo(siginfo, &info); 222 if (ret < 0) 223 break; 224 siginfo++; 225 total += ret; 226 nonblock = 1; 227 } while (--count); 228 229 return total ? total: ret; 230 } 231 232 #ifdef CONFIG_PROC_FS 233 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f) 234 { 235 struct signalfd_ctx *ctx = f->private_data; 236 sigset_t sigmask; 237 238 sigmask = ctx->sigmask; 239 signotset(&sigmask); 240 render_sigset_t(m, "sigmask:\t", &sigmask); 241 } 242 #endif 243 244 static const struct file_operations signalfd_fops = { 245 #ifdef CONFIG_PROC_FS 246 .show_fdinfo = signalfd_show_fdinfo, 247 #endif 248 .release = signalfd_release, 249 .poll = signalfd_poll, 250 .read = signalfd_read, 251 .llseek = noop_llseek, 252 }; 253 254 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, 255 size_t, sizemask, int, flags) 256 { 257 sigset_t sigmask; 258 struct signalfd_ctx *ctx; 259 260 /* Check the SFD_* constants for consistency. */ 261 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); 262 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); 263 264 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) 265 return -EINVAL; 266 267 if (sizemask != sizeof(sigset_t) || 268 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 269 return -EINVAL; 270 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 271 signotset(&sigmask); 272 273 if (ufd == -1) { 274 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 275 if (!ctx) 276 return -ENOMEM; 277 278 ctx->sigmask = sigmask; 279 280 /* 281 * When we call this, the initialization must be complete, since 282 * anon_inode_getfd() will install the fd. 283 */ 284 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, 285 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 286 if (ufd < 0) 287 kfree(ctx); 288 } else { 289 struct fd f = fdget(ufd); 290 if (!f.file) 291 return -EBADF; 292 ctx = f.file->private_data; 293 if (f.file->f_op != &signalfd_fops) { 294 fdput(f); 295 return -EINVAL; 296 } 297 spin_lock_irq(¤t->sighand->siglock); 298 ctx->sigmask = sigmask; 299 spin_unlock_irq(¤t->sighand->siglock); 300 301 wake_up(¤t->sighand->signalfd_wqh); 302 fdput(f); 303 } 304 305 return ufd; 306 } 307 308 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, 309 size_t, sizemask) 310 { 311 return sys_signalfd4(ufd, user_mask, sizemask, 0); 312 } 313 314 #ifdef CONFIG_COMPAT 315 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, 316 const compat_sigset_t __user *,sigmask, 317 compat_size_t, sigsetsize, 318 int, flags) 319 { 320 compat_sigset_t ss32; 321 sigset_t tmp; 322 sigset_t __user *ksigmask; 323 324 if (sigsetsize != sizeof(compat_sigset_t)) 325 return -EINVAL; 326 if (copy_from_user(&ss32, sigmask, sizeof(ss32))) 327 return -EFAULT; 328 sigset_from_compat(&tmp, &ss32); 329 ksigmask = compat_alloc_user_space(sizeof(sigset_t)); 330 if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t))) 331 return -EFAULT; 332 333 return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags); 334 } 335 336 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, 337 const compat_sigset_t __user *,sigmask, 338 compat_size_t, sigsetsize) 339 { 340 return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0); 341 } 342 #endif 343